1. FIELD OF THE INVENTION
The present invention relates to a stapling apparatus, and more particularly to a stapling apparatus which is provided in printing apparatuses such as copying machines, printers and facsimile apparatuses to staple sheets of paper ejected from the printing apparatuses on two or more sheets basis to form sheet bundles.
2. DESCRIPTION OF THE RELATED ART
Hitherto, as a post-processing apparatus each provided in printing apparatuses such as copying machines, printers and facsimile apparatuses, there are known a number of stapling apparatuses each having a stapler for aligning and stapling sheets of paper ejected from the printing apparatus on two or more sheets basis. A recording sheet post-processing apparatus disclosed in Japanese Unexamined Patent Publication JP-A 9-124220 (1997) is provided between a fixing unit in a sheet transporting path of a printing apparatus and an output tray as a sheet tray provided at a sheet ejecting position, and comprises a clinch roller, a press roller, a stopper, a solenoid, and a stapler. The press roller is in press contact with the clinch roller and releases the press contacting force as necessary. The stopper can close the sheet transporting path, which stopper is provided swingably between a recording sheet stop position where the front ends of a plurality of recording sheets come into contact with the stopper, thereby stopping the recording sheets and an open position where the sheet transporting path is opened for conveying a sheet bundle of plural recording sheets to the output tray. The solenoid swings the stopper between the recording sheet stop position and the open position. The stapler is provided movably in the width direction of the recording sheet and staples a plurality of recording sheets whose tips being aligned by the stopper. The clinch roller is driven with a predetermined torque which does not buckle the recording sheet when the tips of the plurality of recording sheets come into contact with the stopper.
The recording sheet which has passed through the fixing unit of the printing apparatus is conveyed under conditions of being sandwiched between the clinch roller and the press roller. The tip of the recording sheet comes into contact with the stopper disposed in the recording sheet stopping position while preventing the recording sheet from being bent by the clinch roller driven with a predetermined torque. The subsequent recording sheets are similarly conveyed and the tips of the recording sheets come into contact with the stopper. The plurality of recording sheets whose tips are aligned by the stopper are stapled by the stapler at a position according to the sheet size, thereby forming a sheet bundle of recording sheets. When the stopper is driven so as to be disposed in the open position by the solenoid, the recording sheet bundle formed by the driving of the clinch roller is placed on the output tray via the opened sheet transporting path. By repeating the operations, a plurality of sheet bundles of recording sheets can be formed.
Japanese Unexamined Patent Publication JP-A 8-239159 (1996) discloses an image forming apparatus with a sorter having a construction such that a plurality of copy sheets are ejected to each of sorter bins of the sorter and the copy sheets in each bin are stapled with a staple.
In a recording sheet post-processing apparatus disclosed in the publication of Japanese Unexamined Patent Publication JP-A 9-124220 (1997), the tips of recording sheets are brought into contact with the stopper for closing the sheet transporting path to stop the recording sheets, and the plurality of recording sheets stopped are bound up, thereby forming a sheet bundle of the recording sheets. The sheet bundle of recording sheets is discharged onto the output tray by the function of the stopper which opens the sheet transporting path. By repeating such operations, a plurality of sheet bundles of recording sheets are formed. Therefore, only the sheet bundles of recording sheets are placed on the output tray.
Meanwhile, a method of ejecting recording sheets onto an output tray and then forming a sheet bundle of the recording sheets can be considered. In this case, in order to form a plurality of sheet bundles of recording sheets, operations of placing recording sheets on a sheet bundle of recording sheets and binding the recording sheets on the sheet bundle have to be performed. It is therefore necessary to move the stapler in the recording sheet stacking direction. The stapler of the prior art is movable in the width direction of the recording sheet but cannot be moved in the recording sheet stacking direction. Consequently, even if the technique is applied to an apparatus for forming a plurality of sheet bundles of recording sheets on the output tray, a plurality of sheet bundles of recording sheets cannot be formed. Since the recording sheet bundle is formed in the sheet transporting path between the fixing part of the printing apparatus and the output tray, there is a case such that the recording sheet bundle is jammed in the sheet transporting path when it is ejected to the output tray. An inconvenience such that the operation of forming the recording sheet bundle is stopped each time the recording sheet bundle is jammed in the sheet transporting path occurs. It is therefore desired to improve the reliability in the formation of the recording sheet bundle.
Since the image forming apparatus with the sorter disclosed in the publication of Japanese Patent Application JP-A 8-239159 (1996) has a structure that a sort bin is provided for each sheet bundle, clearances between the sort bins are dead spaces. There is consequently a problem that only a determined number of sheet bundles can be placed.